This invention relates to a leaf spring cambering apparatus, more particularly to a cambering apparatus for imparting necessary cambers to the leaf blanks for a leaf spring or laminated spring, which requires no change-over of molds in accordance with order changes whereby to drastically reduce change-over time and improve productivity.
Suspension systems consisting of a plurality of leaves 10 which are laminated and bound as shown in FIG. 7 are suitably employed in land transportation vehicles such as railway cars and trucks. Each of the leaves 10 can be prepared, for example, after formation of an eye at one end portion or each end portion of a rolled plate blank having a predetermined thickness or a taper at the other end portion thereof, by subjecting the thus processed blank, which is heated entirely, to a cambering treatment so as to be provided with a predetermined camber. The camber to be imparted to the blank varies depending on the application and load stress: a type in which the camber angle gradually diminishes or increases from the center toward each end and a type in which the middle portion has no camber.
FIG. 8 shows one example of prior art cambering apparatus 12 for imparting a camber to a leaf blank 10. The cambering apparatus 12 basically consists of a cope 14 and a drag 16. The cope 14 is a female mold, whereas the drag 16 is a male mold. A straight leaf blank 10 heated to a hot working temperature is placed between the cope 14 and the drag 16, and then the cope 14 is forced to approach the drag 16 to impart a camber comforting to the profile of these molds.
The mode of manufacturing leaves 10 includes:
(1) Group production mode in which leaves 10 of the same shape and the same specifications are continuously manufactured by the group lot; and
(2) Family production mode in which a main leaf 10 and the other leaves 10 constituting a suspension system are manufactured by the family lot. A suitable production mode is selected by users depending on the application and other factors. In the group production mode, after a predetermined lot number of leaves 10 of the same shape are manufactured, the cope 14 and the drag 16 in the cambering apparatus 12 are changed only when different camber profile is to be imparted in accordance with the order change. It generally takes much time for the change-over of molds, which is a main factor of notably reducing efficiency in cambering leaf blanks 10. Particularly today when small lot production is prevalent, countermeasures must be taken for possible frequent order changes, and it is becoming extremely important to minimize the mold change-over time in the laminated spring industry.
Meanwhile, in the family production mode, each time a leaf blank 10 is cambered, the cope 14 and the drag 16 must be changed, since the camber to be imparted to each leaf blank is slightly different. Accordingly, this mode also suffers a disadvantage in that it requires extremely intricate procedures and consumes a considerable loss time. In this regard, the conventional cambering apparatuses are far from satisfactory for meeting the demand of the industry. Further, various kinds of copes 14 and drags 16 corresponding to the different camber profiles are necessary in both the group production mode and the family production mode, leading to production cost elevation. Moreover, inconveniences can be pointed out that the copes 14 and drags 16 must be stored separately, so that a wide space is required for the storage of these molds and that inventory control becomes troublesome.
On the other hand, the cope 14 and drag 16 wear with time at the molding surfaces and are deformed after a long time of use to be sometimes unable to impart a proper camber to leaf blanks 10. In such cases, while the cope 14 and drag 16 must be repaired or replaced with new ones, which takes a considerable time and is a factor of lowering productivity.